International Union of Official Travel Organisations. (1971). Methodology for annual and medium-term forecasts. International Union of Official Travel Organisations.
Chicago-Zitierstil (17. Ausg.)International Union of Official Travel Organisations. Methodology for Annual and Medium-term Forecasts. Geneva: International Union of Official Travel Organisations, 1971.
MLA-Zitierstil (9. Ausg.)International Union of Official Travel Organisations. Methodology for Annual and Medium-term Forecasts. International Union of Official Travel Organisations, 1971.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.